It's the Fed's Time to Step Up by Christina Romer

Instead, the policy-making committee could adopt the proposal of Charles Evans, the president of the Federal Reserve Bank of Chicago, that the Fed pledge to keep rates near zero until unemployment is down to 7 percent or inflation has risen to 3 percent. Such conditional guidance assures people that the Fed will keep at the job until unemployment is down or the toll on inflation becomes unacceptable. 

(via DeLong)